Bug #92749 JSON arrow operator not wotking with variables and functions
Submitted: 11 Oct 2018 11:28 Modified: 11 Oct 2018 13:37
Reporter: Andrej Thomsen Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: JSON Severity:S3 (Non-critical)
Version:8, 8.0.12 OS:Any
Assigned to: CPU Architecture:Any
Tags: arrow, EXTRACT, json, operator, variable
Triage: Needs Triage: D5 (Feature request)

[11 Oct 2018 11:28] Andrej Thomsen
Description:
The arrow operator doesn't work with functions, strings or variables.
The documentation states the first parameter must be a column but usually such functions are working with variables and function responses as well.

How to repeat:
CREATE FUNCTION passedJson() returns JSON DETERMINISTIC NO SQL return @passedJson;

SET @passedJson= '{"DateRange":{"Start":"2018-11-01","End":"2018-09-30"}}';

SELECT JSON_EXTRACT(@passedJson, "$.DateRange.Start") AS `works`;
SELECT JSON_EXTRACT(passedJson(), "$.DateRange.Start") AS `works`;
SELECT @passedJson->"$.DateRange.Start" AS `doesnt`;
SELECT passedJson()->"$.DateRange.Start" AS `doesnt`;
SELECT  JSON_EXTRACT('{"DateRange":{"Start":"2018-11-01","End":"2018-09-30"}}', "$.DateRange.Start") AS `doesnt`;

Suggested fix:
Enable arrow operators (col->path) and unquoting extraction operators (col->>path) to be used with functions, strings and variables.
[11 Oct 2018 13:37] Umesh Shastry
Hello Andrej,

Thank you for the report!

regards,
Umesh